1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to bio signal measuring, and more particularly, to simultaneously measuring at least two different bio signals without interference.
2. Description of the Related Art
The health condition of a patient can be determined by measuring various bio signals to detect abnormal health symptoms. Commonly, a patient visits a doctor's office and the doctor utilizes medical instruments for measuring bio signals precisely. Recently, to reduce the inconvenience of visiting the doctor's office, research on remote medical treatment has been carried out. Various types of instruments for remotely measuring bio signals have been put on the market. However, if a patient is unskilled, the accuracy of the bio signal measurement is limited. Furthermore, since a plurality of measurement instruments should be purchased to measure many kinds of bio signals, the costs that a patient should pay are very high.
In a conventional bio signal measuring apparatus, sensors for sensing bio signals are connected in an octopus shape to a main body of the apparatus. A user connects by wire or wirelessly bio signal measurement modules, such as a sphygmomanometer, a weight meter, and/or a SpO2 meter, to the main body of the apparatus. After this, items to be measured are selected from a key panel by the user. However, a measurement item should be selected for every measurement, and a measurement mode should be changed for each item. This is troublesome, and the time required for the measurement is increased. Furthermore, since the measurement modules should be connected to the main body, the system is complicated, and thus the costs for implementing the entire system are increased.
Other examples of conventional technologies for bio signal measurement are disclosed in U.S. Pat. No. 5,152,296 and Korean Patent Publication No. 2001-0096186. In U.S. Pat. No. 5,152,296, various sensors are integrated into one sensor module for measuring more items, such as electrocardiogram (ECG), SpO2, and blood pressure signals. This architecture can increase the convenience of measurement in that various bio signals can be measured in one measurement operation. However, since sensors for each measurement item should be separately prepared, costs are still increased, and kinds of measurement items are limited due to spatial constraints of the sensor module. An integrated medical diagnosis apparatus disclosed in Korean Patent Publication No. 2001-0096186 includes a sensor unit constituted by integrating a plurality of sensors for detecting bio signals of a patient and a module unit including changeable and pluggable medical instruments desired by the patient by modularizing a plurality of medical instruments for measuring information corresponding to the bio signals detected by the sensor unit. The apparatus further includes a rear case in which the sensor unit is formed with an external recess. By integrating the sensors for measuring bio signals and modularizing devices for collecting the bio signals measured by the sensors, the user can easily measure his/her bio signals. However, in this case, since the bio signals to be measured are sequentially measured using a selecting switch, the time required for measurement is longer, and it is difficult to simultaneously measure various bio signals at the same time.
Methods of measuring bio signals are largely divided into two categories. First, bio signals naturally generated inside a human body, such as ECG, body temperature, respiration, and pulse, can be directly measured using electrodes. The ECG can be measured using a potential difference between two electrodes contacting the human body, e.g., two electrodes contacting a right end and a left end centering the heart. Second, bio signals, such as body fat, skin resistance, and the amount of blood flow, can be measured by applying a stimulus signal from the outside and receiving a signal responding to the stimulus signal. For example, for the body fat, a stimulus signal is applied through the electrodes contacting both ends, and signals detected from the same electrode or different electrodes are measured, and for the skin resistance, a stimulus signal is applied through an electrode contacting the left end, and a signal detected from the same electrode contacting the left end in response to the stimulus is measured. For signals that can be applied as the stimulus signal, light of a wavelength sensitively responding to each bio signal or a constant alternative current of an optimized frequency for each bio signal can be used. For example, the body fat is optimized to a certain frequency of tens of kHz, and the skin resistance is optimized to a certain frequency between 20 Hz and 50 Hz.
Interference between first and second bio signals does not occur in a case where measurement paths are different when two bio signals having different physical mechanisms are simultaneously measured, e.g., in a case where the first bio signal naturally generated is measured while the second bio signal is measured by irradiating light. However, in a case where the measurement paths are all the same, e.g., in a case where the first bio signal is measured while the second bio signal is measured by applying a current, the measurement cannot be correctly achieved due to the interference between the first and second bio signals.